what are we supposed to say again when christians ask us where we get our morality?

[Whateverist]

The cockroach comparison is an insipid equivocation, as no one has claimed cockroaches have developed society complex enough to require moral codes.

You are wrong. The atheist claim being presented is that morality is a product of evolution. When pressed to explain the response is usually that the adaptation of our species is a disposition to empathy which gives us a reproductive advantage. Where is the morality in that? Sure we form complex social structures. That also is an evolved ability.

The "morality evolved" response is trivial. What it is basically saying is that any behavior that confers a reproductive advantage to the species as a whole is moral by definition. My point is that the same can be said about cockroach survival instincts.Very often, in fact most of the time, moral behaviors require that someone go against their natural instincts. In other words, a person must also apply reason, defer to authorities, or otherwise appeal to something beyond the evolutionary mandates of human nature. Thus evolved dispositions cannot serve as an adequate foundation for morality.

No there are many behaviors which have survival advantage which have nothing whatsoever to do with morality .. the suckling impulse of babies, propensity to pursue fatty and sweet foods, planning cooperative ventures with others, etc.

I don't see why you think you have an advantage here. We point to evolution as giving rise to moral feeling and choices. You point to god. We can just as well ask you whether what god demands is moral because he demands it? Would Abraham have been morally upright to kill his son to please god? If god calls for human sacrifices are those also therefore morally good?

So long as you see something else as underpinning morality one can ask whether morality is anything that a god says it is or which has survival value. But both miss the point.

Morality only has purchase within a society of like minded individuals. If a space ship lands and an alien hops out we wouldn't be justified to assume what counts as decorum for us will overlap what they expect. Likewise there can be subgroups of humans with behavior expectations which don't exactly map our own. What is interesting is that there is as much overlap as there is. You want to say that points to god. I just say that it is because we are more alike than we are different.

You don't have any moral high ground to stand on here, except in your own mind.